1. Field of the Invention
The present invention relates to a head of a bubble type inkjet printer and a method of manufacturing the same, and more particularly, to a head of an inkjet printer and a method of manufacturing the same which is characterized by a method of bonding a heater substrate and a nozzle substrate to form the head.
2. Description of the Related Art
In general, an ink discharge method in an inkjet printer is roughly divided into a bubble-jet type, a Mach-jet type, a thermal printing type and a thermal compression type. Here, the bubble-jet type inkjet printer heats liquid ink by a heat generating device to generate a bubble, and discharges ink using the bubble. In a head of the bubble-jet type inkjet printer, a nozzle plate having a nozzle is disposed on one side of a chamber barrier layer providing an ink chamber, and a heater substrate where a heater is installed is arranged to correspond to the ink chamber and disposed on the other side of the chamber barrier layer.
One example of the bubble-jet type inkjet printer will now be explained with reference to FIG. 1. The conventional head of the inkjet printer includes an ink barrier 40 providing an ink chamber 30, a nozzle substrate 20 including a nozzle plate 21 having a nozzle 23 through which ink is charged, and a heater substrate 10 on which a heater thin film 11 is installed, which is bonded to the nozzle substrate 20 by using the ink barrier 40 made of a polymer as a bonding layer, and which is made of silicon material.
Ink of the ink chamber 30 is heated by the heater thin film 11 and is ejected through the nozzle 23 by a bubble generated by heating the ink. The ink chamber 30 is formed by stacking a photoresist polymer on the heater substrate 10 and by patterning a resulting structure to position the ink barrier 40 in a heater region of the heater thin film 11. The heater substrate 10 and the nozzle substrate 20 are bonded due to heat and pressure by using an adhesive property of the photoresist polymer serving as the ink barrier 40.
When energy is applied to the heater thin film 11 vapor-deposited on the heater substrate 10 to heat ink for 2 to 3 μs, the bubble is formed on the heater thin film 11, and ink of the ink chamber 30 is externally ejected through the nozzle 23 due to a volume and a pressure of the bubble. The ink barrier 40 serves as the bonding layer so that the heater substrate 10 and the nozzle substrate 20 on which a variety of thin films are vapor-deposited can be incorporated. In addition, the ink barrier 40 forms the ink chamber 30 in the heater region. The nozzle plate 21 includes the nozzle 23 for discharging ink corresponding to the heater thin film 11. The nozzle plate 21 is generally made of polyimide or plated nickel. A heatproof layer 12 made of SiO2 is vapor-deposited on the heater substrate 11 to prevent heat of the heater thin film 11 from being discharged. An electrode 13 transmits power to the heater thin film 11. A passivation layer 14 includes an insulating film 14a made of SiN:H and vapor-deposited on the heater thin film, a heater protecting film 14b, and an insulating film 14c made of SiC:H and additionally vapor-deposited to increase durability and chemical resistance of the passivation layer 14.
In a head structure of the inkjet printer, the ink barrier 24 made of the polymer operates as the bonding layer between the heater substrate 10 and the nozzle plate 21 and contacts ink contained in the ink chamber 30. The ink contains at least 60 to 70% of water and soaks into a bulk of the polymer surrounding the ink chamber 22 and a bonding interface of the heater substrate 10, the ink barrier 24 and the nozzle plate 21. This phenomenon expands throughout the polymer and isolates components to cause head defects of the head structure.
In addition, since each ink passage and the ink chamber 30 are filled with a fluid, namely ink, the pressure is transmitted to an adjacent heater chip and other ink passage in an ink discharge, and thus crosstalk is generated to influence bubble formation and ink discharge properties.
In an assembly of the head, the polymer is stacked on the heater substrate 10, then exposed to light and developed, and bonded with the nozzle plate 21. In a case that arrangement is not completely executed in each process, the heater thin film 11, the ink chamber 30 and the nozzle 23 are not precisely aligned to influence directional stability of the ink discharged. As a result, the quality of printing is reduced.